1. Field of the Invention
The present invention relates to the field of implantable electrode leads for delivering electric stimuli from a pulse generator to body tissue and, more particularly, to an adaptor sleeve for a proximal end of such a lead so as to permit connection to pulse generators having sockets of differing sizes.
2. The Prior Art
In the medical electronics industry, particularly the pacing industry, implantable electrode leads are used for delivering electric stimuli from a pulse generator to body tissue. As illustrated in FIG. 1, an electrode 10 has a proximal end 12 for connection to a pulse generator (not shown) and a distal end 14 for being positioned in the desired body tissue. Proximal end 12 has a plug 16, which includes a conducting pin 18, for insertion into a corresponding socket (not shown) of the pulse generator.
In addition to maintaining electrical contact between pin 18 and the pulse generator, an important function of plug 16 is providing secure mechanical coupling to the pulse generator socket. At present, however, there are no standards regulating the size of the plugs and sockets used for these purposes. Generally, the sizes fall into one of two types--large diameter or small diameter. The former is also known in the art as a "high profile" type whereas the latter is known as a "low profile" type.
In an effort to provide compatibility with a wide range of pulse generators having sockets of different sizes, adaptors have been developed for the proximal ends of electrode leads. A typical adaptor, as shown in FIG. 1 and designated by reference character 20, comprises a simple silicone molding fitted over a "low profile-type" plug 16 so as to make the plug resemble a "high profile-type". Thus, a low profile proximal plug can be adapted to fit the socket of a pulse generator designed to accept larger high profile type plugs. The adaptor is conveniently provided with sealing rings and other features associated with proximal plugs and, to ensure internal sealing between the adaptor and proximal plug, suitable sealing rings are provided on the inside of the adaptor or outside of the smaller proximal plug or both.
For practical reasons, electrode leads can be provided with adaptors already fitted on the proximal end, the adaptor being removed at the discretion of the operating physician should the socket of the pulse generator being implanted so require. Removable adaptor sleeves presently known in the art can generally be classified in one of two categories: thin walled adaptors that can be rolled off the proximal plug or rigid type adaptors that are pulled off the plug. FIG. 2 is an example of a thin walled adaptor 22 showing how its end is rolled up so as to remove it from proximal plug 16. FIG. 3 illustrates a rigid type adaptor 24 which includes a reinforced section 26 permitting the physician's fingers to firmly grasp and remove adaptor 24 from proximal plug 16.
Both categories of adaptors suffer from problems, however. Thin walled adaptors (FIG. 2) are typically pre-fitted to the electrode lead; however, removal of such adaptors so as to fit a low profile socket can frequently be difficult due to the resistance of the adaptor to the necessary rolling action. The thicker walled adaptors (FIG. 3) are typically provided as a separate item subsequently fitted over the lead in the operating room by the physician or nurse so as to fit a high profile socket. These are difficult to fit without a lubricant, however, due to the necessary close tolerance with the proximal plug and the internal sealing rings.
A need therefore exists for an adaptor sleeve which is easy to use and can be removed quickly and safely.